Certain individuals who have heart disease do not continuously exhibit abnormal cardiac activity, but rather they do so for brief periods of time at widely spaced intervals. During such periods, such an individual often experiences dizziness, fainting, breathing difficulties, or chest pains. It is extremely difficult for the physician to properly diagnose and treat such cases because symptoms rarely occur when the individual happens to be in the physician's office. See "Detection of Phantom Arrythmias and Evanescent Electrocardiograph Abnormalities", Corday, E. et al. JAMA 193:417, 1965. Two procedures are available for long-term observation of such individuals. The individual can be hospitalized and put under constant observation, including constant monitoring by automatic electronic equipment, or he can be fitted with a portable recording device which captures and records the electrocardiographic data associated with the transient abnormal cardiac event. Because of the expense and inconvenience of hospitalization, the latter procedure is often preferred.
Portable recording devices presently in use for this purpose record the ECG wave continuously, and the resulting mass of data must be thoroughly screened for unusual events and then analyzed for the significance of these events. This requires the use of very expensive and specialized data processing equipment and considerable time of a skilled operator. Moreover, a relatively large amount of data is collected because such equipment operates continuously. Much of this data is not usable because it is obtained when the individual is experiencing normal cardiac activity. U.S. Pat. No. 3,229,687 describes the design and operation of such specialized equipment.